■ 概要
      AS3505K系列是基于CMOS工艺的输出电流为1A*的低消费电流的同步整流型降压DC/DC转换器。
      该芯片由振荡器，电压基准源，误差放大器，开关控制电路，模式控制电路，软启动电路，锁定保护电路，欠压锁定电路(UVLO)，过热关断电路及开关晶体管等组成。这块芯片采用开关器件内置的同步整流的方式，仅加电感和电容即可构成一个高效率的降压DC/DC转换器.由于封装为DFN(PLP)2020−8，因此芯片适用于板级高密度贴装。
      AS3505K系列包含，通过内建的反馈电阻网络以0.1V的步长，±1.5%或18mV的设置输出电压的IC内部固定类型(A,B版本)以及可通过外接电阻网络决定输出电压的可变类型(C版本)。
      另外，可以通过MODE引脚选择不同的工作模式，在轻负载时能自动切换至高效率VFM模式的PWM/VFM自动切换模式，和为了减轻噪声在轻负载时仍然以固定频率控制开关的强制固定在PWM模式的方式。
    内建的保护电路包括了，在每个周期内限制流过LX尖峰电流的电流限流电路和负载电流超过了限流电流或输出端短路的状态持续一定时间后关断锁定内部驱动管的锁定保护电路。若要释放锁定保护状态，把CE使能信号重置，或重置电源电压（电源电压低于欠压锁定检测电压）。电路还内建了过热关断保护电路，如果芯片内部的温度超过了一定值，系统将会重置。
                                                                                      ※）输出电流依赖于工作条件及外部器件，因此这是一个供参考的近似值。

■ 特点
● 消费电流·······················································典型值 40μA(在VFM模式下，无负载)
● 待机电流·······················································值 5μA
● 输入电压范围················································2.3V~5.5V(额定值：6.5V)
● 输出电压范围(A,B版本)·································0.6V~3.3V    (0.1V步进，※0.8V以下的情况，使用条件有限制)
                       (C版本)····································0.8V～3.3V
● 输出电压(A,B版本)·································±1.5%(VOUT≧1.2V)，±18mV(VOUT＜1.2V)
● 反馈电压(C版本)····································±9mV(VFB=0.6V)
● 输出电压/反馈电压温度漂移系数··················±100ppm/°C
● 开关频率·······················································典型值 2.25MHz
● 开关占空比·············································小值 100%
● 内置驱动器导通电阻·····································典型值 P型驱动管 0.23Ω，N型驱动管0.20Ω(VIN=3.6V時)
● 欠压锁定检测电压·········································典型值 2.0V
● 软起动时间····················································典型值 0.15ms
● 内建电感限流电流·········································典型值 1.7A
● 内建锁定保护电路·········································典型值 1.5ms
● 封装·······························································DFN(PLP)2020−8

■ 应用范围
● 使用电池供电的设备
● 照相机，摄像机，便携通讯设备
● WLAN